INJECTION DEVICE

Abstract: An injection device (10) comprising a housing (11) defining a base surface (12), a syringe (15) slidable with respect to the housing (11) having a syringe barrel (16) defining a chamber (21), a hollow needle (20) mounted at one end of the barrel (16) and being in fluid communication with the chamber (21), a plunger (18) slidingly disposed in the barrel (16) for urging fluid from the chamber (21) through the hollow needle (20) and wherein in use the needle (20) of the syringe (15) projects from the base surface (12) at a distance no greater than the depth of skin to be injected and at an angle with respect to the base surface (12) to ensure optimum injection into the skin.

Description: INJECTION DEVICE Technical Field The present invention relates to an injection device having a locating means causing a needle to be inserted into the skin of a subject at a predetermined angle and depth. Whilst the invention is according to one embodiment directed towards and primarily described with reference to skin testing for allergy, it is considered that the invention is suitable for use for injecting other substances into or under skin. Background Skin testing for allergy is conventionally performed by placing a small drop of a solution of the test material (allergen) on the skin (usually forearm or back) of the subject and passing a hypodermic needle or lancet through the drop into the first layer of skin without drawing blood. An inflammatory response in the form of a wheal and flare reaction occurring within about 15 minutes indicates allergy to the suspected allergen. This test, commonly called the "skin prick test" has been used for many years chiefly by specialist allergists as it is labour-intensive and takes a valuable consultation time in a surgery. In addition, it is costly to provide this form of testing, especially if only done occasionally, and requires some technical skill. The method is, however, the most reliable diagnostic procedure for allergies and is sensitive, rapid, specific and relatively inexpensive. Testing for delayed, or cell-mediated hypersensitive reactions may also be performed by skin testing wherein the needle is used to penetrate the skin to a greater depth allowing the test material (antigen) greater access to the tissues underlying the dermal layer. This skin reaction, which is an index of the patient's ability to mount a cellular immune response to the test antigen is usually measured over hours or even days. Given the value and widespread use of skin tests in diagnostic medicine, it is desirable to adapt and standardise the method to make it more available, easy to use and acceptable to both clinicians and patients. Furthermore, it is desirable to improve the speed, reliability and reproducibility of skin test responses. The present methods are cumbersome and laborious for allergy testing. Often large numbers of tests are carried out at one time on the one patient as many allergens are usually tested (for example an individual pollen, house dust mite or fungal species) . The clinician must purchase a bottle of each extract for testing and multiple sampling of these bottles increases the chances of contamination. After placing a drop of the extract on the patient's skin, a needle or lancet is used to administer the sample into the skin. A fresh needle or lancet is required for each extract tested and often involves many extracts. Where 10 to 20 samples must be tested it would be desirable to reduce the time and labour involved for this testing by having an injection device that can administer the desired substance in a controlled manner. Disclosure of Invention In recognising these difficulties with prior art devices, the present invention seeks to provide an injection device which readily allows the controlled and accurate injection of substances into skin of patients and in particular for the use in allergen and delayed-type hypersensitivity testing. The present invention consists in an injection device comprising a housing defining a base surface, a syringe slidable with respect to the housing and having a syringe barrel defining a chamber, a hollow needle mounted at one end of the barrel and being in fluid communication with the chamber, a plunger slidingly disposed in the barrel for urging fluid from the chamber through the hollow needle arid, wherein in use, the needle of the syringe projects from the base surface at a distance no greater than the depth of skin to be injected and at a predetermined angle with respect to the base surface to ensure optimum injection into the skin. The syringe is preferably slidable in a passage in the housing to an extended position wherein the needle projects from the base surface, the passage extending through the base surface, and wherein the extended position is determined by a stop located within the passage of the housing which, in use, engages with a locating portion of the syringe barrel. More preferably the syringe is slidable between the extended position and a retracted position wherein the needle is positioned so as not to project from the base surface. Even more preferably the locating portion of the syringe barrel is in the form of an annular ridge of enlarged diameter located on the outer surface of the syringe barrel which is slidably received in an enlarged diameter portion of the passage of the housing, the enlarged diameter portion having proximal and distal end stops which determine the retracted and extended positions of the syringe respectively. Preferably the injection device is further provided with a spring bias means to urge the syringe into its retracted position. More preferably, the spring bias means is a coil spring located within the enlarged diameter portion of the passage and acting between the locating portion of the syringe barrel and the distal end stop, and wherein, in use the coil spring and the distal end stop determines the extended position of the syringe. Preferably the syringe contains within the chamber a substance to be injected and most preferably the substance is in a fluid form. Optionally the injection device is provided for use in a sterile container with the substance to be injected preloaded in the chamber. The substance to be injected may comprise a composition, an active ingredient, an allergen, an antigen, a drug or any combination thereof. In a preferred embodiment the chamber of the syringe is divided into a distal and a proximal part by means of the seal and, wherein, in use actuation of the plunger causes the seal to be broken and causes the contents within the distal and proximal parts to combine and be urged out through the needle. Preferably, the plunger has a pin extending from its distal end and wherein in use the pin penetrates and breaks the seal causing the contents of the distal and proximal parts to combine. Most preferably, the distal part of the chamber contains a substance to be injected and the proximal part contains a diluent. Most preferably the substance is in a non-liquid form. The injection device is suitable for injecting substances into skin and the angle of the needle with respect to the base surface will be determined by the type of injection to be made by the device. Preferably the injection device of the present invention has the needle defining an angle of less than about 45 degrees relative to the base surface and more preferably the angle of the needle is between 10-30 degrees. Most preferably, the needle of the syringe defines an angle of about 20 degrees relative to the base surface. The distance that the needle projects from the base surface is determined by the type of injection to be made by the device. Preferably the needle projects from the base surface so the end of the needle is 0.5 to 1.5 mm from the base surface. The injection device is suitable for injecting micro-volumes (approximately 5 to 25 microlitres), small volumes (25-100 microlitres) and larger volumes of up to approximately 250 microlitres. The volume of substance to be injected will be determined by the type of injection to be made by the device. It will be appreciated that the base surface can be substantially flat, or can be curved so as to conform with the curvature of the site of injection. The injection device is suitable for injecting substances into or within layers of the skin. Injections may be made to the epidermis (ectodern), dermis (mesoderm) or the subcutaneous fat (adipose tissue). The device may be adapted for different types of injection by varying the angle of the needle to the base surface, the distance that the needle projects from the base and the volume to be injected. Brief Description of Drawings The invention will now be described by non-limiting examples with reference to the following drawings. Figure 1 depicts a perspective view of an injection device in accordance with the present invention with the syringe in its extended position; Figure 2 is a longitudinal-sectional view of an injection device with the syringe in its retracted position and showing one embodiment of the mounting of the syringe on the housing; Figure 3 is a longitudinal-sectional view of an injection device showing embodiment of the mounting of the syringe in the housing; and Figure 4 is a longitudinal-sectional view of the injection device similar to that shown in Figure 2 with an alternative arrangement for containing the substance to be injected. Best Mode for Carrying out the Invention An injection device in accordance with the present invention is identified generally by the numeral 10 in Figs 1-4. The injection device 10 includes a housing 11, a syringe 15 and a needle 20. As shown in Figs 1-4, the housing 11 includes a base surface 12 and a passage 13. A syringe 15 is slidable in the passage 13 of the housing 11. The syringe 15 includes a barrel 16 and a syringe barrel head 17. Within the syringe barrel 16 is situated a plunger 18 including a plunger head 19. The plunger 18 is slidingly disposed within, and is in sealing engagement with the barrel 16 so as to form a chamber 21 towards the distal end of barrel 16. A hollow needle 20 is mounted at the distal end of the barrel 16 and is in fluid communication with the chamber 21. With reference to Fig 2, the syringe 15 is slidable in the passage 13 of the housing 11 to an extended position (as represented by the arrow), wherein the end of the needle 20 is positioned a distance A from the base surface 12. The extended position of the syringe 15 is determined by a stop 22 located within the passage 13 of the housing 11 so as to engage with a portion 26 of the syringe barrel 16 when in use. Stop 22 ensures that needle 20 projects from the base surface 12 at a distance A which is no greater than the thickness of skin to be injected. The positioning of the passage 13 in the housing 11 determines the angle of the needle with respect to the base surface 12 ensuring optimum entry and subsequent injection into the skin. In use, the base surface 12 of injection device 10 is placed on the surface of the skin of a patient and syringe 15 is pushed via pressure on barrel head 17 and/or plunger head 19 through the passage 13 until the barrel 16 is in contact with the stop 22. In doing so the needle 20 penetrates the skin of the patient to the desired depth A. Plunger head 19 is further pressed so as to move the plunger 18 towards the needle 20 and move the contents in chamber 21 through needle 20 into the site of injection. To ensure that the contents of the syringe 15 is not expelled from the needle prior to the insertion into the skin, the resistance of the sliding movement of the syringe 15 in the passage 13 is significantly less than the resistance to the movement of the plunger 18 in the barrel 16. Another embodiment of the mounting of the syringe 15 in the housing 11 is shown in Fig 3 in which the injection device 10 is arranged so that the syringe 15 is slidable between a retracted position and an extended position. In the retracted position the needle 20 is positioned so as not to project from base surface 12 and the positioning of the needle 20 is by a locating means 32 comprising an annular ridge 27 of enlarged diameter located on the outer surface of syringe barrel 16 adapted to be slidably received in an enlarged diameter portion 30 of passage 13 of housing 11. The enlarged diameter portion 30 has end stops 28, 29 which determine the extended and retracted positions respectively of the syringe 15. In order to ensure that needle 20 does not project through the base surface 12 when the device is not in use a coil spring 31 is provided within the enlarged diameter portion 30 to urge syringe 16 into its retracted position. In the embodiments shown in Figs 2 and 3, the substance to be injected is preferably in a liquid form and is contained in the chamber 21. In an alternate embodiment shown in Fig 4, the chamber 21 is divided into a proximal part 14 and distal part 25 by a seal 24. Mounted on the distal end of the plunger 18 is a pin 23 extending towards the seal 24 such that, during actuation of the plunger 18, the seal 24 is broken by the pin 23 and the contents within the distal 25 and proximal 14 parts combine and are urged out through the needle 20. Other means for breaking the seal 24 are also envisaged including pressure of the movement of the barrel 18 towards the seal 24 and the like. The needle 20 is positioned defining angle of less than 45 degrees relative to base surface 12 to ensure that needle 20 penetrates the skin at the required angle. Preferably the angle is 10 to 30 degrees and most preferably the angle is about 20 degrees relative to base surface 12 to ensure optimum entry and injection into the skin of the patient. In order to ensure that the injection device provides for injection of a substance into the skin, it is preferred that the distance A that the end of the needle 20 is spaced from base surface 12 between 0.5 and 1.5 mm. The injection device 10 may be supplied for use preloaded with the substance to be injected and provided in a suitable sterile container. The injection device 10 is easy to use and may be disposable and suitable for the use in skin testing of patients for immediate hypersensitivity (allergic) or delayed hypersensitivity (delayed or cell-mediated) immune reactions. The injection device 10 may contain substances to be injected in liquid form. The substance to be injected may contain suitably formulated and preserved allergen solutions or extracts, antigens, drugs or any combination thereof. Alternatively, the device may be used with a labile or unstable substances which are dissolved or mixed in a liquid diluent in the device immediately before testing. An embodiment as shown in Figure 4 having a chamber 21 divided into two parts enables this form of the invention to be utilised. The injection device 10 may be made of any suitable material such as moulded plastic and needle 20 may be plastic, metal or any other suitable material known to the art. The present invention is also suitable for use in injecting any materials in the skin where a predetermined entry angle of a needle and depth is required for administration of a desired substance. The embodiments of the invention as described above are given by way of example only as constituting preferred forms of the invention defined broadly in the various aspects. It will be appreciated by persons skilled in the art that various numerations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described.

Claims: CLAIMS 1. An injection device comprising: a housing defining a base surface; a syringe slidable with respect to the housing having a syringe barrel defining a chamber; a hollow needle mounted at one end of the barrel and being in fluid communication with the chamber; a plunger slidingly disposed in the barrel for urging fluid from the chamber through the hollow needle; and wherein, in use, the needle of the syringe projects from the base surface at a distance no greater than the depth of skin to be injected and at a predetermined angle with respect to the base surface to ensure optimum injection into the skin. 2. The injection device of claim 1 wherein the syringe is slidable in a passage in the housing to an extended position wherein the needle projects from the base surface, the passage extending through the base surface, and wherein the extended position is determined by a stop located within the passage of the housing which, in use, engages with a locating portion of the syringe barrel. 3. The injection device according to claim 2 wherein the syringe is slidable between the extended position and a retracted position wherein the needle is positioned so as not to project from the base surface. 4. The injection device of claim 3 wherein the locating portion of the syringe barrel is in the form of an annular ridge of enlarged diameter located on the outer surface of the syringe barrel which is slidably received in an enlarged diameter portion of the passage of the housing, the enlarged diameter portion having proximal and distal end stops which determine the retracted and extended positions of the syringe respectively. 5. The injection device according to claim 4 wherein there is further provided a spring bias means to urge the syringe into its retracted position. 6. The injection device according to claim 5 wherein the spring bias means is a coil spring located within the enlarged diameter portion of the passage and acting between the locating portion of the syringe barrel and the distal end stop, and wherein, in use, the coil spring and the distal end stop determines the extended position of the syringe. 7. The injection device according to any one of claims 1 to 6 wherein the syringe contains within the chamber a substance to be injected. 8. The injection device according to claim 7 wherein the substance comprises a composition, an active ingredient, an allergen, an antigen, a drug, or any combination thereof. 9. The injection device according to claim 7 or 8 wherein the substance is in a liquid form. 10. The injection device according to any one of claims 1 to 9 wherein the chamber is divided into a distal and a proximal part by means of a seal, and wherein, in use, actuation of the plunger causes the seal to be broken and causes the contents within the distal and proximal parts to combine and be urged out through the needle. 11. The injection device according to claim 10 wherein the plunger has a pin extending from its distal end and wherein, in use, the pin penetrates and breaks the seal. 12. The injection device according to claim 10 or 11 wherein the distal part contains a substance to be injected and the proximal part contains a diluent for the substance. 13. The injection device according to claim 12 wherein the substance is in a non-liquid form. 14. The injection device according to any one of claims 1 to 13 wherein the needle defines an angle of less than 45 degrees relative to the base surface. 15. The injection device according to claim 14 wherein the needle defines an angle of 10 to 30 degrees relative to the base surface. 16. The injection device according to claim 15 wherein the needle of the syringe defines an angle of about 20 degrees relative to the base surface. 17. The injection device according to any one of claims 1 to 16 wherein the needle projects from the base surface so that the end of the needle is 0.5 to 1.5 mm from the base surface.

Inventors: LE CHEMINANT ERIC, LE CHEMINANT, ERIC
Applicants: CHEMINANT ERIC LE, NORTH SHORE LAB PTY LTD, LE CHEMINANT, ERIC, NORTH SHORE LABORATORIES PTY. LTD.
Application year: 1994
Main classification: A61M5
IPC codes: A61M5